Environmental protection

ABSTRACT

A method of protecting a substrate, which comprises: 
     (a) providing an article having a first portion that has means allowing that portion to be deformed from a larger cross-sectional size to a smaller cross-sectional size and maintained at that smaller size, and that comprises a heat-shrinkable material, 
     (b) positioning the article such that a first portion encloses at least a part of the substrate, 
     (c) deforming the first portion to the smaller cross-sectional size at which it corresponds closely to the part of the substrate, and 
     (d) heat-shrinking the material to cause the first portion of the article to engage the substrate.

BACKGROUND OF THE INVENTION

The present invention relates to the environmental protection ofsubstrates such as cables or pipes, particularly telecommunicationscable splices especially by means that does not require a large input ofenergy for installation.

A cable splice is in general formed by removing insulation from the endsof the cables to be joined, splicing the conductors therein, and formingaround the resulting splice bundle a covering called a splice case, inorder to protect the otherwise exposed conductors. The splice case maybe required to offer protection against water, water vapour, dirt andother contaminants and against animal attack, and should have alife-time comparable to that of the cable insulation, typically at least25 years. Many cables are internally pressurized to keep out watervapour or to provide a means of detecting leaks, and a splice case forsuch cables should also be pressure retaining.

One of the most successful and widely used designs of cable splice isthat marketed by Raychem under the trade marks XAGA and VASM. There aheat-shrinkable sleeve is installed around the splice to be protected,and heat is applied to cause it to shrink down into engagement with thecables either side of the splice. A propane torch is usually used toapply the heat. In order to provide further mechanical strength and,where desired to provide further resistance to water vapour penetration,an internal liner may be provided around the splice bundle. Such a linerand sleeve are disclosed in GB 1431167 (Raychem). These sleeves may beinternally-coated with a hot-melt adhesive.

Whilst this type of splice case is simple to install and has excellentperformance, it has the disadvantage in requiring the use of a torch forinstallation. Where a cable to be spliced runs in, for example, a ductor manhole shared with gas pipes or where the substrate to be protectedis itself a gas pipe the use of a torch is undesirable and may beforbidden.

Attempts have been made to overcome this problem by providing anelectrical source of heat, although that too may be unacceptable if thevoltage required is sufficiently high that a short could cause sparking.Also, large, heavy, power supplies may be needed since access to mainspower cannot be relied upon. A large amount of power is required sincethe sleeve must be heated to cause it to shrink, and any adhesivecoating has to be heated to cause it to melt or otherwise to beactivated.

One electrical solution is disclosed in DE 2136739 (Siemens AG). There asplice case comprises two semi-cylindrical thermoplastic half-shellshinged together along respective edges, allowing the splice case to beclosed like a clam-shell around the splice to be protected.

U.S. Pat. No. 4,085,286 (Raychem) discloses a splice case havingpreformed shrinkable outlets having self-contained electrical heaterscomprising a conductive polymer having a positive temperaturecoefficient of resistance (PTC). A PTC heater as part of a shrinkablesleeve is disclosed in EP 0117762 (Raychem).

EP 0236056 (Raychem) discloses a non-shrinkable splice case comprising aflexible sealing bag that is seam-sealed by a hot-melt adhesiveactivated by a self-contained, self-regulating, strip heater.

Heat shrinkage is desirable, of course, since a sleeve or otherprotective article can easily be installed around a cable etc. since itcan be supplied over-size. Close tolerances in manufacture can beavoided, and a single size of article can be used over various sizes ofcables. After this preliminary installation the article is heat-shrunkcausing it to engage the substrate and causing leak paths between it andthe substrate to be eliminated. This is particularly useful where anoutlet of an article is to be sealed to a cable etc. that passes throughit. A problem arises, however, if the heater that is used to bring aboutheat-shrinkage is other than a flame, a hot-air gun, or a very hightemperature radiative heater; and this problem is due to the changingdimension of the shrinking article. Somehow the heater must follow thearticle down as it shrinks since contact between the heater and thearticle will in general be necessary.

For this to occur the heater must be flexible and in particular must beable to shrink or be able to collapse under the force of the shrinkingarticle. A heater having diamond shaped slots for this latter purpose isdisclosed in U.S. Pat. No. 4,177,446 (Raychem). EP 0117762 (Raychem),mentioned above, employs a heater which itself shrinks.

I have noticed a further problem resulting from shrinkage of thearticle. One reason a large supply of heat is required is that thearticle will not in general be thermally-insulated, it being difficultto provide an insulating housing that shrinks along with the sleeve.

Furthermore, I have realized that it is possible to retain the benefitsof heat-shrinkage, but avoid the disadvantages of what may be termed a"bulk" or "large-scale" change of dimension. Thus, a heater and aninsulating housing may be provided that do not change size and which,with a small amount of power, cause localized shrinkage of an articlewhich before shrinkage has a configuration which corresponds closely tothat of the substrate to be protected.

SUMMARY OF THE INVENTION

Thus, the invention provides a method of protecting a substrate such asa cable splice, which comprises:

(a) providing an article such as a sleeve, particularly a wraparoundsleeve, having a first portion (for example an end portion or otheroutlet) that has means, preferably corrugations particularly extendinglongitudinally of the sleeve, allowing that portion to be deformed froma larger cross-sectional size to a smaller cross-sectional size andmaintained at that smaller size, and that comprises a heat-shrinkablematerial,

(b) positioning the article such that the first portion encloses atleast a part of the substrate,

(c) deforming (preferably by bunching together corrugations thereof) thefirst portion to the smaller cross-sectional size at which itcorresponds closely to the part of the substrate,

(d) heat shrinking the material to cause the first part to engage thesubstrate,

(e) optionally positioning an electrical heater in thermal contact withthe heat-shrinkable material and activating the heater to cause theheat-shrinkage of the step (d), and

(f) optionally and generally before step (d) enclosing the first portionwithin a heat insulator.

When I refer to the first part being deformed such that its sizecorresponds closely to that of the substrate, I mean that a significantpart and preferably a majority of the change in dimension required isbrought about in that way, thereby reducing the change that is requiredduring the heat-shrinking step. Preferably, however, substantially allof the bulk dimensional change is brought about that way. Where thefirst part is corrugated (by which term I include the provision of meanssuch as lines of weakness to aid subsequent corrugation at step c), thetroughs of the corrugations will, after step c, touch the substrate.Thus, although the material may still be shrinkable by its full amount,that shrinkage will not result in a change in diameter or whatever ofthe article. The effect of shrinkage will, in general, be to remove thecorrugations, thereby removing any leak paths that would otherwise existthrough them.

A sealing material, such as a hot-melt adhesive, or otherwiseheat-activatable material, may be provided between the substrate and thearticle. Such a material may be provided as a coating on the articleand/or as a separate article, for example in sheet form, particularly asa tape wrap.

Also or alternatively, a heater, particularly an electrical heater maybe provided which too is preferably positioned between the article andthe substrate. The heater is also preferably in sheet form, particularlyas a tape wrap, and may be provided as part of the same article as thesealing material. The heater may comprise a battery, which may generateheat through its internal resistance and/or through an externalresistive heating element.

Such a heating article may be used independently of the method definedabove, and the invention therefore also provides an article forprotecting a substrate (either on its own, or by facilitating theinstallation of some other article) which comprises a flexible sheetcomprising:

(a) a battery, preferably an alkali-metal battery, such as one based onlithium.

(b) a heat activatable sealing material,

(c) a resistive heating element, which may comprise the internalresistance of the battery,

(d) means whereby the battery can be electrically connected to theheating element to cause the heating element to become hot,

(e) optionally a device, which may comprise element (c), having apositive temperature coefficient of resistance connected in series withthe battery and in thermal contact with the element (c),

Step (c) of the method preferably brings the first portion of thearticle down onto the heating article that has previously been wrappedaround the substrate. Then, an insulating housing made for example offoam, optionally as foam half-shells, is placed around the deformedfirst portion and held in place for example with tie wraps. The heateris then activated causing the sealing material to become activated andthe material of the first portion to shrink.

The means in the article of the method allowing deformation preferablyallows the formation of a substantially frusto-conical portion at oradjacent one or each end of the sleeve, said substantiallyfrusto-conical portion being formed in step (c).

Preferably, that means allows formation of a substantiallyfrusto-conical portion adjacent one or each end of the sleeve, andtapering towards that end, and a substantially cylindrical portionbetween that end and the narrow end of the frustum, said substantiallyfrusto-conical and cylindrical portions being formed in step (c).

The means allowing deformation may comprise corrugations (by which termwe include lines of weakness or other means through which corrugationsarise when the article is deformed). Thus, deformation may give rise tocorrugations proper, or may merely cause existing corrugations tobunch-up, and thus adopt a certain size.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further illustrated with reference to the accompanyingdrawings, in which:

FIGS. 1A and 1B show a conventional prior art, heat-shrinkable sleevearound a cable splice;

FIGS. 2A and 2B show a prior art shrinkable corrugated tape forenvironmental sealing;

FIGS. 3A and 3B show a prior art shrinkable corrugated tape forenvironmental sealing;

FIGS. 4A, 4B and 4C show the installation of a sleeve by the method ofthe invention;

FIGS. 5A, 5B and 5C show a heating tape wrap; and,

FIGS. 6A, 6B and 6C show switching means included in a battery tapewrap.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1A and 1B show the most widely used shrinkable telecommunicationscable splice cases, namely those marketed under the Raychem trademarksXAGA and VASM. A cable splice 1, which may be quite bulky due to a largenumber of conductor connectors, joins two cables 2. A liner 3 is wrappedaround the splice in order to provide further protection. The liner 3may have crowned ends which can be deformed to provide frusto-conicalends to the liner. The splice case is completed by a heat-shrinkablepolymeric sleeve 5 that is wrapped-around the liner and secured in itswrapped-around configuration by bring together rails 6 and sliding overthem channel 7. The sleeve is then shrunk by applying heat, generallyusing a propane torch, such that it engages the liner and the cables ateach side of the splice. The finished splice case is shown in FIG. 2B.

The corrugated material shown in FIGS. 2A, 2B and 3A, 3B is disclosed inEP 42262 (Raychem). Shrinkability is induced into a material by a firstexpansion which is unidirectional but uniform and then by a secondexpansion which produces corrugations 8, which may increase in extentacross the surface of the material. The material can be used to coverpipe branch-offs or splice cases. The material is wrapped to form asleeve 5 around a branch pipe 9 in order to seal its junction with amain pipe 10. The corrugated region is then splayed out to form a collar11 which can overlie a hole in the main conduit.

FIGS. 3A and 3B show a substrate having a transition from a largerdiameter at 12 to a smaller diameter at 13. A tape 14 havingcorrugations 8 is wrapped around the substrate and then heated. FIG. 3Bshows the smooth cover that results after installation.

The invention is illustrated in FIGS. 4, 5 and 6.

FIGS. 4A, 4B and 4C show various stages in the installation of aheat-shrinkable sleeve 5 around a splice between cables 2 to form asplice case.

In FIG. 4A the sleeve 5 has been wrapped around the splice and the rails6 are about to be secured together with channel 7. Some sealingmaterial, for example a gel, may be used to improve sealing between therails 6.

End portions of the sleeve have corrugations 8 therein, and in theembodiment illustrated the corrugations are provided in two portions 15and 16 at each end, optionally separated by some form of discontinuity.When the ends of the sleeve are deformed by radial compression (forexample by hand) frusto-conical portions will be formed corresponding toportions 15 and cylindrical portions will be formed corresponding toportions 16. The frusto-conical portions will produce a taper down fromthe bulky splice to the cables 2, and the cylindrical portions will liealong the cable or cables 2. Thus, the end portions of the sleeve can bemade to conform closely to the size of the cables.

Before the deformation is carried out, however, tape wraps 17 areinstalled around the cables. These tape wraps may comprise one or moreof a battery, a heating element, and a sealing material. Electricalleads 18 are shown by means of which a battery within wrap 17 can beactivated, or by means of which an external power source can beconnected to a heating element within wrap 17.

After deformation of the portions 15 and 16 down onto the wraps 17, athermal housing 19 may be applied and secured with tie wraps 20.

This is the situation shown in FIG. 4B. FIG. 4B also shows furtherelectrical leads whereby leads 18 are connected to an external powersupply, which supplies power to cause heat-shrinkage of the regions 16.A portion of the sleeve between portions 15 (or that portion togetherwith at least part of portions 15) is preferably not heat-shrinkable.

After shrinkage is complete the thermal insulation may be removed. Theresult is shown in FIG. 4C, where the corrugations can be seen to havebeen removed from portions 16. Also shown in FIG. 4C is a branch-offclip 21 which has been used to form or maintain a plurality of conduitsin an end portion of the sleeve 5. An excellent hot-melt bond can thusbe made between the sleeve 5 and the cables 2 with very littleelectrical power. For typical splice case sizes a more than adequatepower output of a battery within each tie wrap 17 would be 5-30 watthours, particularly 10-20, say about 15 watt hours. I prefer that acurrent of 5-35, especially 10-20 particularly about 20 amps bedelivered to a PTC heating element within the wrap which autotherms tomaintain the temperature between 110° and 130° C. An installation oftime of less than 10 minutes, probably about 7 minutes, may be readilyachieved.

FIGS. 5A, 5B and 5C show a preferred cable wrap employing a lithiumbattery. A cable wrap may be made having sections such that it can becut to length in the field. For example it could be produced in-linehaving sections such that, say, one section was suitable for a cable ofabout 15 mm diameter and that four sections would be needed for a cableof 80 mm diameter, and 2 or 3 sections be needed for intermediate sizes.The tape could be 20-60 mm, say about 50 mm, wide and each section beabout 50-80 mm, say about 70 mm long. The preferred dimensions couldresult in a heat output of just above 3 watt hours per section.

A tie wrap 17 is shown in FIG. 5A. It is coated with a hot-melt adhesive22 on each side. Electrical leads 18 are connected to the anode and thecathode of the internal battery, and as a result connection together ofleads 18 causes current to flow through the internal resistance of thebattery and any other heating element within the wrap. That causes thewrap to become hot and the adhesive 22 to be activated.

A cross-section through the wrap is illustrated in FIG. 5B. One can seea lithium electrode 23, a porous membrane 24, an electrolyte 25, and amagnesium dioxide or other suitable electrode 26.

The tie wrap 17 shown in FIG. 5C also has a PTC heating element 28connected in series with the lithium battery. Heat is generated at leastin part within the element 28 which, due to its PTC behaviour, regulatesthe heat output of the strip.

The conductors 18 have been connected together as shown at 27 to causethe internal battery 23,24,25,26 to power the internal PTC heatingelement 28.

FIGS. 6A, 6B and 6C show a way in which the battery may be electricallyconnected to a heating element, be it either its own internal resistanceor a separate element.

The cable wrap illustrated, in perspective in FIG. 6A and incross-section in FIGS. 6B and 6C, comprises a PTC heating strip 29 and alithium battery 30 together with a switching means 34,35,36. Slits orother means 31 may be provided in one or more components to improveflexibility of the strip allowing it to be wrapped around a cable.

An aluminum or other electrode 32,33 is provided on each side of thePTC/battery laminate. When these two electrodes are connected together,an electric circuit is made and current will flow through the PTC strip29 causing the cable wrap to become hot. At one edge of the strip thetwo electrodes protrude, and are separated by an insulator 34. Aninsulating clip 35 retains the electrodes 32,33 close to one another,but on opposite sides of the insulator 34. When the clip is pulled tothe right as drawn in FIG. 6B the electrodes move with it to a positionaway from the insulator 35. In this position, as shown in FIG. 6C, theelectrodes can now touch one another, optionally under the influence ofthe clip 35 which forces them together. The electrodes may be providedwith corrugations 36, allowing their extension to the right.Alternatively, the electrodes may remain fixed, and an insulator moved.

For the avoidance of doubt it is here noted that the invention providesa method and articles for environmental protection which allow a highquality seal to be made under a heat-shrinkable sleeve, but avoid thebulk change of dimension usually associated with heat-shrinkablesleeves. Thus the amount of heat required is reduced. Any one or more ofthe sleeve configurations, heaters, power supplies, switches or sealingmaterials disclosed may be selected.

I claim:
 1. A method of protecting a substrate, which comprises:(a)providing an article having a first portion that comprises a heatshrinkable material, said heat shrinkable material additionally havingmeans allowing said first portion to be mechanically deformed from alarger cross-sectional size to a smaller cross-sectional size, (b)positioning the article such that said first portion encloses at least apart of the substrate, (c) mechanically deforming said first portions tothe smaller cross-sectional size at which it corresponds closely to saidpart of the substrate, and (d) subsequently heat-shrinking said heatshrinkable material to cause said first portion to engage said part ofthe substrate.
 2. A method according to claim 1, in which the meansallowing deformation comprises corrugations.
 3. A method according toclaim 2, in which the first portion comprises a sleeve and thecorrugations run substantially longitudinally of the sleeve.
 4. A methodaccording to claim 1, in which the article comprises a sleeve, and themeans allowing deformation allows the formation of a substantiallyfrusto-conical portion at or adjacent one or each end of the sleeve,said substantially frusto-conical portion being formed in step (c).
 5. Amethod according to claim 4, in which the means allowing deformationallows the formation of a substantially frusto-conical portion adjacentone or each end of the sleeve and tapering towards that end and asubstantially cylindrical portion between that end and the narrow end ofthe frustum, said substantially frusto-conical and cylindrical portionsbeing formed in step (c).
 6. A method according to claim 1, in which thestep (c) results in the first portion having corrugations therein of acertain size.
 7. A method according to claim 6, in which step (d)results in at least partial removal of the corrugations.
 8. A methodaccording to claim 5, in which step (c) results in the substantiallyfrusto-conical and cylindrical portions having corrugations therein of acertain size, and step (d) results in substantially complete removal ofthe corrugations from the substantially cylindrical portion.
 9. A methodaccording to claim 1, in which a sealing material is positioned beforestep (c) between the substrate and the first portion.
 10. A methodaccording to claim 9, in which the sealing material comprises a hot-meltadhesive.
 11. A method according to claim 1, which additionallycomprises:(e) positioning an electrical heater in thermal contact withthe heat-shrinkable material and activating the heater to cause theheat-shrinkage.
 12. A method according to claim 11, in which the heateris positioned before step (c) between the substrate and the firstportion.
 13. A method according to claim 11, in which the heaterincorporates its own power supply.
 14. A method according to claim 13,in which the heater comprises a battery.
 15. A method according to claim14, in which the battery is activated by shorting it across its internalresistance.
 16. A method according to claim 15, in which a device havinga positive temperature coefficient of resistance is connected in seriesbetween the battery and the short and in thermal contact with thebattery.
 17. A method according to claim 14, in which the battery isactivated by connected a resistive heating element across it.
 18. Amethod according to claim 17, in which the element has a positivetemperature coefficient of resistance.
 19. A method according to claim18, in which the element comprises a conductive polymer.
 20. A methodaccording to claim 11, in which the heater has the form of a tape wrap.21. A method according to claim 20, in which the tape wrap comprises(i)the heater (ii) a sealing material; and (iii) a control device.
 22. Amethod according to claim 1, which additionally comprises:(f) enclosingthe first portion within a heat-insulator.
 23. A method according toclaim 22, in which the insulator comprises a foam.
 24. A methodaccording to claim 1, in which the substrate comprises a cable.
 25. Anarticle suitable for carrying out a method according to claim 3.